Problem 2.2

The fluid is incompressible.

Radial and tangential velocity components are zero.

Streamlines are parallel.

Cylindrical geometry.
Problem 2.3

The fluid is incompressible.

axial velocity is invariant with axial distance.

Plates are parallel.

Cartesian geometry.
Problem 2.4

The fluid is incompressible.

Radial and tangential velocity components are zero.

Streamlines are parallel.

Cylindrical geometry.
Problem 2.5

Shearing stresses are tangential surface forces.

 xy and  yx are shearing stresses in a Cartesian coordinate system.

Tangential forces on an element result in angular rotation of the element.

If the net external torque on an element is zero its angular acceleration will vanish.
Problem 2.6

Properties are constant.

Cartesian coordinates.

Parallel streamlines: no velocity component in the y-direction.

Axial flow: no velocity component in the z-direction.

The Navier-Stokes equations give the three momentum equations.
Problem 2.7

Properties are constant.

Cylindrical coordinates.

Parallel streamlines: no velocity component in the r-direction.

Axial flow: no velocity component in the  -direction.

No variation in the  -direction. The Navier-Stokes equations give the three momentum
equations.
Problem 2.8

Properties are constant.

Cartesian coordinates.

Two dimensional flow (no velocity component in the z-direction

The Navier-Stokes equations give two momentum equations.
Problem 2.9

Properties are constant.

Cylindrical coordinates.

Two dimensional flow (no velocity component in the  -direction.

The Navier-Stokes equations give two momentum equations.
Problem 2.10

Motion in energy consideration is represented by velocity components.

Fluid nature is represented by fluid properties.
Problem 2.11

Properties are constant.

Cartesian coordinates.

Parallel streamlines: no velocity component in the y-direction.

Axial flow: no velocity component in the z-direction.
Problem 2.12

Properties are constant.

Cartesian coordinates.

Parallel streamlines: no velocity component in the y-direction.

Axial flow: no velocity component in the z-direction.

The fluid is an ideal gas.
Problem 2.13

This is a two-dimensional free convection problem.

The flow is due to gravity.

The flow is governed by the momentum and energy equations. Thus the governing
equations are the Navier-Stokes equations of motion and the energy equation.

The geometry is Cartesian.
Problem 2.15

The flow is due to gravity.

For parallel streamlines the velocity component v = 0 in the y-direction.

Pressure at the free surface is uniform (atmospheric).

Properties are constant.

The geometry is Cartesian.
Problem 2.16

This is a forced convection problem.

Flow properties (density and viscosity) are constant.

Upstream conditions are uniform (symmetrical)

The velocity vanishes at both wedge surfaces (symmetrical).

Surface temperature is asymmetric.

Flow field for constant property fluids is governed by the Navier-Stokes and continuity
equations.

If the governing equations are independent of temperature, the velocity distribution over
the wedge should be symmetrical with respect to x.

The geometry is Cartesian.
Problem 2.18

The geometry is Cartesian.

Properties are constant.

Axial flow (no motion in the z-direction).

Parallel streamlines means that the normal velocity component is zero.

Specified flux at the lower plate and specified temperature at the upper plate.
Problem 2.19

The geometry is cylindrical.

No variation in the axial and angular directions.

Properties are constant.
Problem 2.20

The geometry is cylindrical.

No variation in the angular direction.

Properties are constant.

Parallel streamlines means that the radial velocity component is zero.
Problem 2.21

The geometry is cylindrical. (ii)

No variation in the axial and angular directions.

Properties are constant.
Problem 2.22

This is a forced convection problem.

The same fluid flows over both spheres.

Sphere diameter and free stream velocity affect the Reynolds number which in turn affect
the heat transfer coefficient.
Problem 2.23

This is a free convection problem.

The average heat transfer coefficient h depends on the vertical length L of the plate.

L appears in the Nusselt number as well as the Grashof number.
Problem 2.24

This is a forced convection problem.

The same fluid flows over both spheres.

Sphere diameter and free stream velocity affect the Reynolds number which in turn affect
the heat transfer coefficient. (iv) Newton’s law of cooling gives the heat transfer
Problem 2.25

Dissipation is important when the Eckert number is high compared to unity.

If the ratio of dissipation to conduction is small compared to unity, it can be neglected.
Problem 2.26

The plate is infinite.

No changes take place in the axial direction (infinite plate).

This is a transient problem.

Constant properties.

Cartesian coordinates.
Problem 2.27

The plate is infinite.

No changes take place in the axial direction (infinite plate).

This is a transient problem.

Constant properties.

Cartesian coordinates.

Gravity is neglected. Thus there is no free convection.

The fluid is stationary.